A. Field of Invention
This invention pertains to the construction of pneumatic tires and more specifically, to methods for constructing pneumatic tires with functionally graded belts.
B. Description of the Related Art
In general, the construction of a radial ply tire involves the fabrication of a carcass with bead rings and sidewalls on a cylindrical drum followed by forming the carcass into a toroidal shape. One or more belt plies are then wrapped sequentially around the outer circumference of the carcass after which a tread is applied to the carcass on top of the belt. The “green” or uncured tire is then transferred to a tire mold where it is formed under pressure into a final shape and then cured or vulcanized.
It is well known that the particular belt used in the construction of the tire has a significant impact on the performance of the tire. Each belt is formed of one or more belt plies. Typically, each belt ply is reinforced with a plurality of closely spaced cords embedded in uncured rubber, the cords generally extending at an angle of between 15 degrees to 30 degrees with respect to the equatorial plane of the tire. When two belt plies are used, generally the cord angles are equal but aligned in opposite directions with respect to the equatorial plane. The cords used in belt plies may be formed of various materials including nylon, polyester, rayon, cotton, aramid and steel.
One recent advancement in tire belt construction is the use of segmented belts. A segmented belt includes at least one belt ply that is axially divided or segmented. U.S. Pat. Nos. 6,394,160 and 6,444,070, which have a common assignee and are fully incorporated herein by reference, describe a tire with a segmented belt and a method of constructing such a tire.